1. Field of the Invention
The present invention relates to a rotary-type magnetic recording medium where servo patterns are formed in servo pattern regions on both one surface and another surface of a disk-shaped substrate by patterns with recording regions and non-recording regions, a recording/reproducing apparatus equipped with such magnetic recording medium, and a stamper capable of manufacturing such magnetic recording medium.
2. Description of the Related Art
As one example of a recording/reproducing apparatus equipped with this type of magnetic recording medium, Japanese Laid-Open Patent Publication No. 2006-31856 discloses a magnetic disk drive (hereinafter simply “disk drive”) equipped with a double-sided patterned disk medium (hereinafter simply “magnetic disk”) for perpendicular magnetic recording. On the magnetic disk provided in this disk drive, servo regions and data regions (hereinafter also referred to as “servo pattern regions” and “data recording regions”) are provided with mirror symmetry on both the upper surface (“one surface”) and the lower surface (“another surface”) of a glass substrate. Annular magnetic tracks (so called “discrete tracks”) are formed with a predetermined track pitch in the radial direction in the data recording regions of this magnetic disk. On this magnetic disk, magnetic tracks are formed by forming a recording layer (a magnetic layer) in convex shapes on an underlayer formed on the glass substrate, and non-magnetic guards (in this example, air) are provided between magnetic tracks that are adjacent in the radial direction.
In addition, a preamble portion, an address portion, and a burst portion (also referred to hereinafter as the “preamble pattern region”, “address pattern region”, and “burst pattern region”) are provided in the servo pattern regions on the magnetic disk. Also, on this magnetic disk, in respective regions inside each servo pattern region (hereinafter, when no distinction is required, the respective regions inside a servo pattern region are referred to as “functional regions”), in the same way as the magnetic tracks inside the data recording regions, magnetic layers (hereinafter, referred to as “convex magnetic portions”) are formed in convex shapes on the underlayer formed on the glass substrate and non-magnetic portions (in this example, air) are provided between adjacent convex magnetic portions so that a servo pattern is formed of “prebits”. On this magnetic disk, the servo patterns are formed in the respective functional regions so that the formation positions of the convex magnetic portions and non-magnetic portions match one another on the one surface and the other surface of the glass substrate (i.e., both surfaces are mirror images of each other).
Note that the state referred to by the expression “the formation positions match one another” in the present specification refers to a state where the recording regions (i.e., convex magnetic portions) are formed at formation positions on the other surface (or the one surface) corresponding to the formation positions of the recording regions (convex magnetic portions) on the one surface (or the other surface) and the non-recording regions (i.e., non-magnetic portions) are formed at formation positions on the other surface (or the one surface) corresponding to the formation positions of the non-recording regions (non-magnetic portions) on the one surface (or the other surface).
Also, by applying a magnetic field in a direction so as to pass through the thickness of the magnetic disk during the manufacturing of this magnetic disk, the convex magnetic portions on the entire one surface and other surface of the magnetic disk are all DC magnetized (direct current-magnetized) in the same direction (in this example, from the one surface toward the other surface in the thickness direction of the magnetic disk). This means that on this magnetic disk, the convex magnetic portions on the one surface are DC-magnetized in the thickness direction from the surface of the magnetic disk toward the inside in the thickness direction, for example, and the convex magnetic portions on the other surface are DC-magnetized in the thickness direction from the inside of the magnetic disk in the thickness direction toward the surface. Accordingly, in a disk drive equipped with this magnetic disk, it is possible for a CPU to magnetically read a servo pattern from each servo pattern region (i.e., each functional region) on the one surface and the other surface via a magnetic head and extract servo data. By doing so, tracking servo control is carried out based on the extracted servo data.